Electronic device for regulating the voltage of alternators, particularly for motor vehicles

ABSTRACT

An alternator for a motor vehicle is provided with an electronic device for regulating output voltage. The field winding of the alternator is energized through a power circuit controlled by an SCR triggered by a control circuit when voltage drops below a preset value. The triggering signal to the SCR and initial flow in the field winding through the SCR is governed by-the control circuit. Initial current flow in the field winding also takes place through an indicator lamp connected for battery recharging. The control circuit output applied to the SCR is also connected through a diode to the anode of a medium power SCR connected to one phase of the alternator.

United States Patent Basso et al. Oct. 24, 1972 [54) ELECTRONIC DEVICEFOR [56] References Cited REGULA'IING THE VOLTAGE OF uurmo STATESPATENTS ALTERNATORS PARTICULARLY FOR 3,568,041 3/1971 Arakane................320/o4s x MOTOR VEHICLES inventors: Eugenio Bill),Levioo; Guglielmo Ravaachh, Geneva; Vittorio Frangilli, Gallarate, allof Italy Fabbrica Italian: Mqnetl Marelli S.p.A., Milano, Italy Filed:April 8, 1971 Appl. No.: 132,515

Assignee:

Foreign Application Priority Data April ll, 1970 Italy ..23183 A170Primary Examiner-J. P. Miller Assistant Examiner-Robert J. HickeyAttorney-Ostrolenk, Faber, Gerb & Soifen [57] ABSTRACT An alternator fora motor vehicle is provided with an electronic device for regulatingoutput voltage. The field winding of the alternator is energized througha power circuit controlled by an SCR triggered by a control circuit whenvoltage drops below a preset value. The triggering signal to the SCR andinitial flow in the field winding through the SCR is governed bythecontrol circuit. Initial current flow in the field winding also takesplace through an indicator lamp connected for battery recharging. Thecontrol circuit output applied to the SCR is also connected through adiode to the anode of a medium power SCR connected to one phase of thealternator.

2Clalms,3Drawing figures Z. z L[ LL i XI I I," l I n l 5 I U L I #2 2 nI i f H i 4 I H iii I I L J PATENTEDucI 24 m2 SHEEI 2 0F 2 4 7 VIA 16 1ELECTRONIC DEVICE FOR REGULATING THE VOLTAGE OF AL'I'ERNATORS.PARTICULARLY FOR MOTOR VEHICLES This invention relates to improvementsin electronic 5 circuits for regulating the voltage of alternators,particularly for motor-vehicles, wherein the field winding is suppliedby the alternator through a power circuit controlled by a siliconcontrolled rectifier (SCR), the

latter being triggered by a signal from a control circuit when the linevoltage drops below a predetermined value.

In such known regulating circuits, the silicon controlled rectifier isconnected in the power circuit,

whereby this SCR should be a power silicon controlled rectifier with theaccompanying disadvantages in cost and dissipated energy.

Moreover, in these circuits, in order that the alternator may deliverpower at the initial stages of its opera- 2 tion, the alternator fieldwinding is initially supplied by the battery through a circuit includinga resistor which, however, remains connected during the normal operationof the regulator, thus causing an unnecessary power dissipation.

Therefore, these regulators are subjected to substantial heating,thereby requiring housings fitted with cooling fins or other expedientsin order to assure an effective heat dissipation to the outside. Ofcourse, this will increase the bulk of these devices in addition to thecost thereof.

It should also be noted that conventional regulating devices require theprovision of a further special circuit to obtain a signalling forbattery recharging and possible field winding short-circuits.

It is the object of the present invention to provide an improved voltageregulating circuit avoiding the abovementioned disadvantages.

According to the invention, this is accomplished by a circuit whereinsaid silicon controlled rectifier (SCR) is used only to supply thecontrol signal to the power circuit and the initial current to the fieldwinding. Accordingly, due to low currents being involved, this SCR maybe a low power silicon controlled rectifier.

The power circuit consists of power lines connecting all or somealternator phases with the field winding through a corresponding mediumpower silicon controlled rectifier controlled by said low power SCR.

According to a very important aspect of the invention, the initialenergization of the field winding and signalling for battery rechargingand short-circuits in field winding can be provided through an indicatorlamp simply connected between the lower power SCR and field winding.

Further advantages and features of the invention will become apparentfrom the following description as referred to the appended drawingsshowing, by mere way of not limiting example, some preferred embodimentsof the voltage regulator, and more particularly:

FIG. 1 shows the battery recharging wiring diagram comprising athree-phase alternator provided with a voltage regulating circuit inaccordance with the invention; and

FIGS. 2 and 3 are two modified forms of the regulating circuit shown inFIG. 1.

Referring to FIG. 1 showing a battery recharging circuit arrangementparticularly suited for motorvehicles, the following elements arerespectively designated: alternator A, battery 8, utilizing circuit Uand voltage regulating circuit R in accordance with the invention.

The alternator is a three-phase alternator, the stator windings of whichare star connected. However, it is apparent that the alternator may be athree-phase alternator having delta stator windings, or singleortwophase alternator, etc. F,, F, and F, are the windings for the threephases, numerals l, 2 and 3 are the three outputs connected through athree-phase rectifier bridge to line L, and E is the field or excitingwinding of the altemator.

The voltage regulator R in FIG. 1 utilizes two phases of the alternator,but whichever is the number of utilized phases, it typically comprisesthree portions hereinafter indicated with reference to the embodimentshown:

1. a low-power control section responsive to line voltage and comprisingin a per se known manner a resistive divider RJRo, R P and R andtransistor TR, the emitter of which is connected through R, to line Land through Zener diode D2 to ground for voltage stabilization;

2. a control section for the power circuit comprising the siliconcontrolled rectifier SCR, controlled through diode D and the set ofresistors R R R R and R and finally 3. a power section or circuitcomprising the silicon controlled rectifiers SCR and SCR connected inthe circuits connecting the alternator phases with the field winding E,and diode D The low power control section may be other than that shownprovided that it is capable of triggering the silicon controlledrectifier SCR when the voltage on line L drops below a predeterminedvalue.

in the diagram, the two power circuits are supplied by the alternatorphases F and F, and the corresponding silicon controlled rectifiers SCRand SCR, are connected through their anodes to the outputs l and 2 ofsaid phases F, and F and through their cathodes to termine] 4 of fieldwinding E. The control gates of said silicon controlled rectifiers SCR]and SCRZ are then connected to the SCR cathode through resistors R, andR respectively.

From the foregoing, it will be appreciated that only the very lowcurrents for triggering diodes SCR, and SCR, and initially supplying thefield winding E flow through SCR.

Therefore, SCR is a low power silicon controlled rectifier with evidentadvantages in cost and dissipated power which are reduced. It is alsoapparent that said winding E is supplied by a plurality of power linescontrolled by SCR. Thus, moderate or medium power silicon controlledrectifiers as SCR, and SCR, can be used also for such lines.

A further highly significant feature of the regulating circuit accordingto the invention consists of combining the battery recharging andshort-circuits winding E signalling circuit.

For this signalling, it is only needed to connect an indicator lamp Sbetween terminal 5 connected to the cathode of SCR and terminal 4 ofwinding E, as shown in the diagram. Through the connection of this lampa further flow is developed for initial supply current to winding Eprovided by battery B through SCR. The charging indicator circuit iscompleted by diode D the anode of which is connected to the output forthe low power control section and more particularly to the collector ofTR, and the cathode of which is connected to the anode of the siliconcontrolled rectifier of the power circuit which is the first to becomeconductive. Phase F is assumed to be the first conductive phase and,therefore, the anode of SCR, is connected to the D, cathode.

As set forth in the following, any flashings of lamp S are avoided by D,during normal operation of the regulator.

The operation of the regulating circuit R in FIG. I will now bedescribed.

When switch I is closed, and the alternator is stationary, the batteryhas a lower voltage than the regulator setting voltage, which may beadjusted by means of potentiometer P The base of transistor TR is thenat a lower potential than that of the emitter, as stabilized by Zenerdiode D,, and therefore said transistor becomes conductive. Then, asignal is applied through the decoupling diode D1 to the gate" electrodeof SCR, causing the latter to be triggered.

Upon SCR being conductive, a low current is supplied to the fieldwinding E both through li -R and Rg-Rg and through the indicator lamp S,if any, which lights, signalling that the battery B is supplyingcurrent. Moreover, sufiicient voltages are present on the gates of SCR,and SCR, for causing the triggering thereof.

After starting and as soon as the alternator rotor has attained asufficient speed, alternating voltages appear on the anodes of SCR, andSCR, as generated by the phases F and F, rendering these siliconcontrolled rectifiers conductive, the latter thus beginning to supplycurrent to the field winding E. As excitation increases, the rectifiedoutput voltage of the alternator on line L is increased until it exceedsthe battery voltage and attains the predetermined setting value.

At this time, the conduction of SCR stops, since two identical voltagesappear on the anode and cathode and, therefore, the indicator lamp isswitched off.

On the other hand, when the setting voltage has been attained and as thebase of TR is at a higher voltage than the emitter, the collectorcurrent is zero and, as a result, the signal on the gate" of SCR isremoved.

Due to the 120 phase shift of the two voltage waves applied to theanodes of SCR, and SCR, and since SCR, is the first to becomeconductive, as above assumed, in the absence of biasing on the gate" ofsaid diodes, and as soon as the voltage on the anode of SCR is zero, thecurrent supply to the field winding E will be fully interrupted, thuscausing the output voltage on line L to drop almost immediately. Thisvoltage drop will cause the re-operation of the low power controlsection, enabling the medium power elements SCR,, SCR, to conduct forre-energizing the field winding.

The repetition of this cylce, with times depending on the loadconditions of the utilizing circuit and the engine speed, will regulatethe average level of the excitation current and stabilize the outputvoltage to the preset value.

As above stated, when the generator supplies current, the indicator lampis connected between two points, the potential of which is identical orzero, thereby evidently causing the switching off thereof.

However, for the correct operation of the lamp the diode D2 isessential. Thus, it will be seen that when SCR, and SCR; are conductive,the associated voltage waveforms with respect to ground, at the outputof the generator phases and hence also on the cathodes of said siliconcontrolled rectifiers are phase shifted.

Accordingly, for some fraction of a period, there will be no voltage onthe field winding E. Therefore, at this fraction, SCR could be enabledto conduct by the control circuit, should the line voltage be below thepre-set value, thus supplying the indicator lamp. On the contrary, byconnecting the diode D SCR is cut off during this short time interval,by by-passing to ground the signal applied on its gate", thus preventingthe lamp supplying circuit from being re-closed. Said lamp S alsoindicates short-circuits occurring in winding E. Thus, when such acondition occurs, terminal 4 is grounded, while terminal Sis at linevoltage and, therefore, lamp S is switched on.

Some components aiding in good operation of the regulator are also shownin the diagram of FIG. I. The negative temperature coefiicient resistorR0 is for accommodating the value of the regulated line voltage to thebattery requirements.

The comparatively high rate capacitor C provides a time constant to thecontrol circuit so as to render it unaffected by the changes at highfrequency in the line voltage.

Diode D is for shorting to ground the negative overvoltages on the fieldwinding which may be built up upon current interruption therein.Capacitor C, is for reducing the slope of the field winding transients.

The circuit and operation for the regulator in H6. 1, using only twophases of the alternator for supplying the winding E, have beendescribed.

It is apparent that the foregoing substantially applies also to theregulators in FIGS. 2 and 3, relating to the use of one phase only orall three phases of the alternator, respectively.

lt will be seen that in the diagram of FIG. 3 the diode D, is omitted;the omission of this component is possible since the use of all threephases of the alternator causes a voltage, which is substantially thesame as line voltage, to be applied on the field winding during the fullwave period.

The invention has been shown in connection with some particularcircuits, but it is evident that all the equivalent solutions orpossible modifications and changes in the circuits as necessary inaccordance with practical requirements are within the spirit of theinvention.

The embodiments of the invention in which an exclusive privilege orproperty is claimed are defined as follows.

1. Electronic apparatus for controlling a multiphase alternator having afield winding and a plurality of stator windings and a field winding,said apparatus comprising:

a pilot lamp and a first silicon controlled rectifier connected inseries with said field winding and the output of said alternator;

a voltage supply comprising a battery coupled to said alternator;

a control section coupled between said voltage supply and said firstsilicon controlled rectifier and responsive to changes in said voltagesupply for triggering the operation of said first silicon consaidcontrol section including a low power rating trolled rectifier;transistor for coupled to the control electrode of at least two supplylines coupled to said stator said first silicon controlled rectifierwhereby said windings; first silicon controlled rectifier significantlya plurality of second silicon controlled rectifiers, 5 red es he c rrentOutput OfSaid transistor.

each having their outputs coupled to an associated An electronic deviCeas Claimed in Claim supply li d h i th i i t l d i wherein the amount ofsupply lines connecting the almon to id fi ld i di temator to the fieldwinding is less than the amount of each of said plurality of siliconcontrolled rectifiers altfimatol' Phases, f further comprising {nodemeans having comm] electrodes; said control elemrodes 10 coupled betweensaid control section transistor and the being coupled in common to saidfirst silicon conionnecmm Petween P of plurality of sl'hcon troned tifitrolled rectifiers and its associated supply lme of the said firstsilicon controlled rectifier having a control Stator winding whlch thefirst to conductelectrode;

1. Electronic apparatus for controlling a multiphase alternator having afield winding and a plurality of stator windings and a field winding,said apparatus comprising: a pilot lamp and a first silicon controlledrectifier connected in series with said field winding and the output ofsaid alternator; a voltage supply comprising a battery coupled to saidalternator; a control section coupled between said voltage supply andsaid first silicon controlled rectifier and responsive to changes insaid voltage supply for triggering the operation of said first siliconcontrolled rectifier; at least two supply lines coupled to said statorwindings; a plurality of second silicon controlled rectifiers, eachhaving their outputs coupled to an associated supply line and havingtheir inputs coupled in common to said field winding; each of saidplurality of silicon controlled rectifiers having control electrodes;said control electrodes being coupled in common to said first siliconcontrolled rectifier; said first silicon controlled rectifier having acontrol electrode; said control section including a low power ratingtransistor for coupled to the control electrode of said first siliconcontrolled rectifier whereby said first silicon controlled rectifiersignificantly reduces the current output of said transistor.
 2. Anelectronic device as claimed in claim 1, wherein the amount of supplylines connecting the alternator to the field winding is less than theamount of alternator phases, and further comprising diode means coupledbetween said control section transistor and the connection between oneof said plurality of silicon controlled rectifiers and its associatedsupply line of the staTor winding which is the first to conduct.